Biodiesel Titration Limits
Why Titrate Biodiesel?
- The process of making biodiesel is essentially removing glycerine from oil and replacing it with methanol. Glycerine is removed using an alkaline catalyst such as potassium or sodium hydroxide. However, biodiesel made from old cooking oil often contains free fatty acids (FFA) that need to be extracted and turned to soap prior to creating the diesel. Titrating the oil will determine how much FFA is in the oil so that extra catalyst can be added.
Levels of Sodium Hydroxide
- Generally, 3.5 grams of sodium hydroxide (NaOH) is used for a liter of clean, non-acidic oil. If you need 3 milliliters of NaOH to neutralize your oil, then you will need an additional 3 grams of NaOH per liter, or 6.5 total grams per liter. Much will depend on the purity of your NaOH, so be sure to check your package for its relative purity. Ninety-nine percent pure is common for lye, but potassium hydroxide is lower, between 90 and 91 percent.
- You can use phenolphthalein, methyl orange or litmus to test acidity, or pH. pH indicators change their color at a certain acidity or alkalinity. Litmus changes color between a pH of 5 and 8, the higher number indicating alkalinity. A pH of 7 is considered neutral. Phenolphthalein indicates alkalinity around 8.3 and methyl orange changes color at a higher acidic level: 4.4. Of these methods, phenolphthalein is the best indicator of an alkaline solution.
Disposing Waste Glycerin
- Using sodium hydroxide in titration and then in the final batch of biofuel will create a waste product that is toxic. Potassium hydroxide, on the other hand, will result in a compostable waste product that is not only clean to dispose of, but potentially beneficial to your garden. Another option is to take the raw glycerol and mix it with coarse sawdust and pour it into a small cardboard carton or box. You can use this as a log in the fire, a wood-burning stove or when you go camping.